Conventionally, a compressor is a device for compressing a fluid such as air and refrigerant gas. The compressor includes a motor unit installed in the hermetic container for generating driving force, and a compression unit for sucking and compressing gas by receiving the driving force of the motor unit. In the compressor, if a power source is applied to generate the driving force in the motor unit, the driving force is transmitted to the compression unit, thereby sucking, compressing, and discharging gas in the compression unit.
A reciprocating compressor is a device, in which a piston is coupled to an armature of a reciprocating motor as a unit without a crank axis. FIG. 1 shows an embodiment of the conventional reciprocating compressor.
As shown in FIG. 1, the conventional reciprocating compressor comprises a ring shaped frame 1 supported by an elastic supporting member (not shown) in a casing V; a cylindrical cover 2 fixed at one side surface of the frame 1; a cylinder 3 fixed as a horizontal direction in the middle of the frame 1; an inner stator assembly 4A fixed at an outer circumference surface of an inner side of the frame 1 supporting the cylinder 3, and an outer stator assembly 4B fixed at an inner circumference surface of an outer side of the frame 1 apart from the outer circumference surface of the inner stator assembly 4A with a predetermined air-gap; an armature 5 inserted in the gap between the inner stator assembly 4A and the outer stator assembly 4B for consisting of the armature of the reciprocating compressor; a piston 6 fixed to the armature 5 as a unit for sucking and compressing refrigerant gas by having a slidable movement at the inner portion of the cylinder 3; an inner resonant spring 7A supported at one side surface of the frame 1 and at an inner side of the armature 5 unified with the piston 6 for having a resonant movement; an outer resonant spring 7B supported at an inner side surface of the cover 2 and at an outer side of the armature 5 unified with the piston 6 for having a resonant movement; and a discharge valve assembly 8 mounted at an end portion of a discharge side of the cylinder 3 for limiting a discharge of the compressed gas at the time when the piston 6 reciprocates.
Unexplained reference numeral 8a denotes a discharge valve, 8b denotes a spring for supporting the discharge valve, 8c denotes a discharge cover, SP denotes a suction pipe, and DP denotes a discharge pipe.
The conventional reciprocating compressor is operated as follows.
That is, if an electric current is applied to the inner and outer stator assemblies 4A and 4B and the movable 5 has a linear reciprocation, the piston 6 coupled to the armature 5 linearly reciprocates in the cylinder 3, thereby generating a pressure difference in the cylinder 3. By the pressure difference, refrigerant gas in the casing V is sucked in the cylinder through a refrigerant flow passage F of the piston 6, compressed, and discharged, which is repeated.
In the meantime, FIG. 2 is a perspective view showing a suction valve coupling structure for a reciprocating compressor in accordance with the conventional art, and FIG. 3 is a sectional view showing a suction valve coupling structure for a reciprocating compressor in accordance with the conventional art.
As depicted, a suction valve 9 for limiting a suction of refrigerant gas which passed through the refrigerant flow passage F and a refrigerant suction hole 6e is fixed to a frontal surface of a head portion 6b of the piston 6 by a fixation bolt B.
Also, the suction valve 9 is formed as a thin disc plate corresponding to an end portion surface S of the head portion 6b of the piston 6.
A cut-off 9c of an opened curve line shape is formed in the disc plate, and has a shape of a question mark, in which the disc plate is divided into a circle shaped part and a ring shaped part.
The circle shaped part constitutes a fixation portion 9d coupled to the head portion 6b of the piston 6, and the ring shaped part corresponding to an outer portion of the circle shaped part constitutes an open/close portion 9a for opening and closing the refrigerant suction hole 6e. In the meantime, the suction valve 9 is made from high carbon spring steel which is generally used, and the piston 6 is made from cast iron having an excellent foundry characteristic.
A structure for coupling the suction valve 9 to the piston 6 is as followings. First, a screw hole 6d is formed in the middle of the end portion surface S of the head portion 6b of the piston 6, and a through hole 9b for coupling the valve is formed at the fixation portion 9d of the suction valve 9. Then, under a state that the through hole 9b of the suction valve 9 and the screw hole 6d of the piston 6 are unified, the suction valve 9 is coupled to the piston 6 by inserting the fixation bolt B.
However, in the conventional suction valve coupling structure, since the suction valve 9 formed as a thin plate is coupled by the fixation bolt B, the fixation bolt is minutely loosened in a process that the suction valve 9 is repeatedly opened and closed, which causes a slip rotation of the suction valve 9. According to this, the suction valve deviates from the refrigerant suction hole 6e, thereby lowering a reliability of the compressor.
Also, since a head portion of the fixation bolt B is protruded at an inner portion of the compression space P, a dead volume is generated. According to this, not only compression efficiency is lowered, but also a precise location sensing of an upper dead point and a lower dead point of the piston 6 is not possible by the protruded head portion of the fixation portion B, thereby having a problem to control a stroke for a reciprocal movement of the piston 6.